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PIG. 65.

Preparation of Hydrogen Chloride.A filter flask
(J, litre) is fitted with a rubber cork, through which a tap-
funnel is inserted. The flask is filled one-third full of con-
centrated hydrochloric acid and is attached to a wash-bottle
containing' a little concentrated sulphuric acid. A delivery
tube is attached to the wash-bottle. The hydrogen chloride is
generated by dropping concentrated sul-
phuric acid from the tap-funnel into the
flask containing the hydrochloric acid.
As the gas is rapidly absorbed by the
alcohol and may in consequence run
back into the wash-bottle, it is advis-
able to run in the acid rather more
quickly at the beginning than is neces-
sary later on and to generate the gas
for a short time before passing it into
the alcohol. The apparatus is shown
in Fig. 65.
When saturated, the mixture is boiled
for an hour with reflux condenser on
the water-bath and filtered hot from the ammonium chloride
which remains undissolved. On cooling, the greater portion of
the ester hydrochloridc crystallises. A further quantity may be
obtained by concentrating the mother liquors. Yield 3035
J*r<>/>tT//cs.~ Colourless needles ; m. p. 144, soluble in hot
alcohol, very soluble in water.
G-lycocoll Ester Hydrochloride from Gelatine.
Mix 100 grams commercial gelatine or size with 300 c.c. con-
centrated hydrochloric acid and shake until the gelatine is nearly
dissolved ; then add a few fragments of porous pot and boil
over wire gau/e with reflux condenser for four hours. The
dark coloured product is now evaporated on < the water-bath
under diminished pressure in the apparatus shown in Fig. 66.
It consists of two distilling flasks (i litre) fitted together by
rubber corks, the one acting as distilling flask and the other as
receiver. The receiver which is cooled by a stream of water
is attached to a water-jet aspirator. A long capillary, which
nearly touches the bottom of the flask, is inserted through the